Handwheel Torque Limitor

ABSTRACT

A torque limiting device with an override mechanism coupled to a valve assembly capable of limiting the torque applied to the valve assembly and selectively being overridden to permit the application of excessive torque to the valve assembly. Tattletale devices capable of indicating when an override mechanism has been activated can also be integrated with the torque limiting device.

TECHNICAL FIELD

The present invention generally relates to valves and the operation ofvalve devices. More specifically, particular embodiments of the presentinvention relate to methods and apparatuses for limiting an amount oftorque applied to an actuator, a valve, or a valve device.

BACKGROUND

Actuators and valve assembly components may be operated or driven bydevices such as handwheel assemblies. The rotation of a handwheel ineither a clockwise or counter-clockwise direction imparts a rotationalforce on a drive shaft, which in turn, operates an actuator or valveassembly. For example, a handwheel device typically used to driveactuators and valve assemblies is illustrated in FIG. 1. Rotation of thehandwheel drives a stem in or out of an actuator housing or valveassembly, thereby driving components contained therein. The use ofhandwheels and handwheel devices with actuators and valve assemblies iswell known.

Actuators and valve assemblies driven by handwheels are typicallysubject to torque limitations. Application of torque beyond the torquelimits of an actuator or valve assembly can damage the actuator or valveassembly. Once an excessive amount of torque has been applied to anactuator or a valve assembly, the device should be replaced.

To prevent damage caused by the excessive application of torque,warnings are usually printed in the user manuals that accompany theactuators or valve assemblies. In other instances, warnings may also beplaced on actuator housings or on handwheels attached to an actuator inorder to discourage an over-application of torque to the assembly.During operation, however, it is difficult, if not impossible, for anoperator to monitor the amount of torque being applied to an actuator orvalve assembly. This is especially true when an operator can onlyestimate the amount of torque that is being applied to a device based ontheir experience and on a feel for the amount of force that is beingapplied at any given time.

In many cases, there is no mechanism to prevent the application of anexcessive amount of torque to an actuator or a valve assembly. Moreoften than not, when excessive torque is applied to an actuator or valveassembly, the excessive torque causes damage to the actuator or valveassembly, resulting in the need for maintenance or replacement of theactuator or valve assembly. Therefore, it would be desirable to providea mechanism by which an operator could be prevented from imparting anexcessive amount of torque to an actuator or valve assembly by operationof a handwheel.

Although the application of excessive force and torque to an actuator orvalve assembly is undesirable, emergency situations may arise whichrequire such application. In those instances, the ability of an operatorto override a mechanism preventing the application of an excessiveamount of torque should not be hindered.

Furthermore, in many cases where damage to an actuator or valve assemblyis caused by the application of excessive torque to a device, themanufacturer may be called upon to fix the device. The inability of themanufacturer to determine whether a device was damaged due to theapplication of an excessive amount of torque to the device or whethersome other legitimate damage occurred is troublesome. Therefore, it isdesirable to provide a mechanism by which manufacturers may monitor ordetermine when damage to an actuator or valve assembly has been causedby the application of excessive amounts of torque to the device ratherthan by a defect or normal wear-and-tear of the device.

Therefore, there is a need to provide a mechanism that limits the amountof torque applied to an actuator or valve assembly. It is also desirableto provide a mechanism for overriding or disengaging a torque limitingdevice so that excessive amounts of torque may be applied to an actuatoror valve assembly if the need for such excessive torque is required. Inaddition, it is desirable to provide a mechanism that indicates when atorque limiting device has been disengaged or overridden.

DISCLOSURE OF INVENTION

According to embodiments of the present invention, a torque limitingdevice is provided with a valve assembly. Torque limiting devicesaccording to embodiments of the present invention may limit the amountof torque applied to a valve assembly by an actuator or a handwheel.

According to some embodiments of the present invention, a torquelimiting device may be affixed to a handwheel mechanism of a valveassembly to regulate the amount of torque that may be applied to thestem of the valve assembly by movement of the handwheel mechanism. Inother embodiments, the torque limiting device may be affixed to anactuator associated with a valve assembly to regulate the amount oftorque that may be applied to the stem of the valve assembly by theactuator.

In some embodiments, the torque limiting device may include aslip-clutch device capable of being disengaged when a predetermined orpreset torque regulation limit has been reached, thereby preventingfurther application of torque to the valve stem. Upon the application ofan acceptable torque limit, the slip-clutch may re-engage, therebyallowing torque to be applied to the stem of the valve assembly.

According to other embodiments of the present invention, the torquelimits of the torque limiting device are adjustable. In someembodiments, the torque limit may be adjusted by altering the number ofsprings positioned in a spring set compartment of the torque limitingdevice. In other embodiments, shims may be added to or removed from thespring set compartment, thereby increasing or decreasing the torquelimitations of the torque limiting device. In still other embodiments ofthe present invention, the torque limits may be adjusted by adjustingthe position of a pressure nut of the torque limiting device, which, inturn, adjusts the pressure on springs and/or shims contained in a springset compartment. A pressure nut may be loosened or tightened withrespect to the spring set compartment to assert a force on the springsand/or shims contained within the spring set compartment. Further, thetorque limits may be adjusted by adding or removing shims between ashell of the torque limiting device and an attachment bolt attaching apressure nut to the torque limiting device. The distance between thepressure nut and the shell of the torque limiting device may dictate theamount of space within the spring set compartment, thereby dictating theamount of force applied to the springs and/or shims within the springset compartment, which, in turn, provides the torque limits for theslip-clutch device.

In still other embodiments of the present invention, a torque limitingoverride mechanism is provided, wherein the torque limiting overridemechanism allows the torque limiting device to be disengaged, bypassed,or otherwise removed. In some instances, activation of the torquelimiting override mechanism allows torque above the set limits to beexerted on the stern of a valve assembly by a handwheel, an actuator, orother device. In some embodiments, the torque limiting overridemechanism, once engaged, cannot be disengaged. The permanently engagedtorque override mechanism provides evidence that the torque limits ofthe valve assembly may have been exceeded. In other embodiments, thetorque override mechanism may be disengaged.

Tattletale devices capable of indicating when the torque limits of atorque limiting device have been exceeded are provided in otherembodiments of the invention. In some embodiments, the tattletale devicemay be visible upon external inspection of an operating torque limitingdevice. In other embodiments, evidence of the tattletale may only appearupon disassembly of the torque limiting device. The presence of thetattletales allow valve manufacturers to determine if the torque limitsof the valve assemblies may have been exceed at some previous time.Thus, when presented with a warranty claim or a failed valve assembly,the valve manufacturer can identify one possible source of the damage,which may limit warranty work or the manufacturer's liability.

BRIEF DESCRIPTION OF DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming that which is regarded as the present invention,this invention can be more readily understood and appreciated by one ofordinary skill in the art from the following description of theinvention when read in conjunction with the accompanying drawings inwhich:

FIG. 1 illustrates a valve and handwheel assembly as known in the art;

FIG. 2 illustrates a cross-sectional view of the components of ahandwheel valve assembly including a torque limiting device according toparticular embodiments of the present invention; and

FIG. 3 illustrates a particular embodiment of a slip-clutch for use withtorque limiting devices of the present invention.

BEST MODE(S) FOR CARRYING OUT THE INVENTION

Embodiments of the present invention relate to torque limiting devicesand more particularly to torque limiting devices capable of beingcoupled with or otherwise associated with a handwheel or actuator tolimit torque applied by the handwheel or actuator to a valve assembly.In some embodiments, the torque limiting devices may include a torquelimiting override mechanism capable of being activated to allow thetorque limiting device to be bypassed. In still other embodiments,torque limiting devices of the present invention may include a“tattletale” device capable of indicating whether the torque limits ofthe torque limiting device have been previously exceeded.

A torque limiting device 300 according to some embodiments of theinvention is illustrated in FIG. 2. The torque limiting device 300 maybe used with a valve assembly 200 and a handwheel 100 or, alternatively,an actuator (not shown), to limit the amount of force applied to thevalve assembly 200 by use of the handwheel 100 or actuator. The torquelimiting device 300 may be attached to the valve assembly 200 and thehandwheel 100 or actuator such that the rotation of the handwheel 100 oractuator to drive the valve assembly 200 is limited by the torquelimiting device 300.

A torque limiting device 300 according to embodiments of the presentinvention may include a housing 310 that is attached to the valveassembly 200. The housing 310 includes an opening therein to accommodatea valve stem 210 or other portion of a valve assembly 200, which may beacted upon by the torque limiting device 300. Within an interior spaceof the housing 310, the torque limiting device 300 can include aslip-clutch device 320, a drive mechanism 380 in communication with atleast a portion of the slip-clutch device 320, one or more springs 350applying a force to the slip-clutch device 320, and a restraining device(such as, for example, a pressure nut 360) defining the upper portion ofthe space wherein the springs 350 are located within the housing 310 andin communication with a handwheel 100 or an actuator.

According to particular embodiments of the invention, the handwheel 100and the slip-clutch device 320 are in communication such that therotation of the handwheel 100 or actuator creates rotation of at least aportion of the slip-clutch device 320. The rotation of the slip-clutchdevice 320 may, in turn, operate on the drive mechanism 380 to move astem 210 or other component of the valve assembly 200. The springs 350of the torque limiting device 300 limit the amount of torque that may beapplied to the drive mechanism 380 to move the stem 210 by allowing theslip-clutch device 320 to slip when a predetermined torque is reached orexceeded.

Some embodiments of the present invention include a slip-clutch overridemechanism, the details of which are described in more detail hereafter.The slip-clutch override mechanism enables disengagement of theslip-clutch device 320, allowing the transfer of torque from thehandwheel 100 or actuator to the stem 210 without any limitations. Insome embodiments, the slip-clutch override mechanism may not bedisengaged after being activated without performing maintenance on thetorque limiting device 300 and the valve assembly 200. In otherembodiments, the slip-clutch override mechanism may be disengaged but a“tattletale” device or indicator is triggered by the activation of theslip-clutch override mechanism, thereby providing an indication that thetorque limits of the device may have been exceeded.

According to particular embodiments of the invention, the torquelimiting device 300 may be coupled between a valve assembly 200 and ahandwheel assembly 100, as illustrated in FIG. 2. In other embodiments,a torque limiting device 300 may be coupled between a valve assembly 200and an actuator (not shown). The torque limiting device 300 limits theamount of torque that a handwheel 100 or actuator applies to the stem210 of the valve assembly, helping to prevent damage to the valveassembly due to excessive application of torque to the handwheel 100. Inother embodiments, the torque limiting device 300 may be configured tolimit the amount of torque being applied to the handwheel 100 or anactuator by the stem 210 of the valve assembly.

The torque limiting device 300 illustrated in FIG. 2 includes a housing310 which is removably fixed to a valve assembly 200 by one or morebolts 315 or other fastening devices. The housing 310 includes anopening on an end fixed to the valve assembly and an opening at anopposing end, wherein the openings provide sufficient space for a stem210 of a valve assembly 200 to be positioned through the openings andinto the valve assembly 200. The housing 310 also defines an interiorspace. Moveable and fixed parts positioned within the interior spacelimit the amount of torque that can be applied to the stem 210 and,thus, the valve assembly 200.

According to some embodiments of the present invention, a packingmaterial 390 may be positioned within a portion of the interior space ofthe housing 310. The packing material 390 may be used as a fill materialwithin the housing 310 so that torque limiting devices 300 may beconfigured to fit different sized actuators and valve assemblies.

A drive mechanism 380 may also be positioned within a portion of theinterior space of the housing 310. The drive mechanism 380 may sit inthe interior space and include grooves, tongues, threads, or otherfeatures capable of moving a stem 210 having threads. For example, thedrive mechanism 380 may include a hole in its center with grooves on theinner surface of the center hole, which grooves are matched to fit thethreads of a stem 210 being used with the valve assembly. Rotation ofthe drive mechanism 380 within the interior space acts on the threads ofthe stem 210, thereby moving the stem 210 upwards or downwards inresponse to the rotation of the drive mechanism 380.

In some embodiments of the present invention, a slip-clutch device 320can be positioned in the interior space of the housing 310, positionedover, and removably connected to the drive mechanism 380. When moved,the slip-clutch device 320 causes the rotation of the drive mechanism380, which in turn moves the stem 210 of the valve assembly. In otherembodiments, the drive mechanism 380 may be incorporated with theslip-clutch device 320, thereby eliminating a need for an additionalcomponent in the torque limiting device 300.

In some embodiments of the present invention, a slip-clutch device 320may include a drive plate 322 and a slip plate 324, as illustrated inFIG. 3. The drive plate 322 may include one or more receiving grooves323 or other receptors configured to receive projections 325 of the slipplate 324. The drive plate 322 and the slip plate 324 may be positionedsuch that the projections 325 sit within the receiving grooves 323. Whenpositioned in such a manner, the two plates may move as a single unit.The drive plate 322 may be removably attached to the drive mechanism 380such that movement of the drive plate 322 invokes movement of the drivemechanism 380. Alternatively, the drive plate 322 may include thecomponents of the drive mechanism 380 such that a separate drivemechanism 380 is not required.

The drive plate 322 may include multiple receiving grooves 323.According to some embodiments of the present invention, the drive plate322 includes one or more such receiving grooves for accepting orreceiving a projection 325 of the slip plate 324.

The receiving grooves 323 may be identical to each other or individualreceiving grooves 323 may include different configurations. By way ofexample and not limitation, a drive plate 322 may include two receivinggrooves 323: a first receiving groove having a first size and a secondreceiving groove having a second size. The corresponding slip plate 324may include two projections 325 having different configurations: a firstprojection having a configuration capable of mating with the firstreceiving groove and a second projection having a configuration capableof mating with the second receiving groove, but not the first receivinggroove. Thus, in order to properly mate and rotate the slip-clutchdevice 320, the first projection must sit in the first receiving grooveand the second projection must sit in the second receiving groove. Uponthe application of an excessive amount of torque to the torque limitingdevice 300, the first and second projections will slip out of the firstand second receiving grooves, respectively, causing the slip-clutchdevice 320 to disengage and discontinue rotation of the drive mechanism380. When disengaged, rotation of a handwheel or actuator will continueto rotate the slip plate 324 until the projections 325 of the slip plate324 again sit in corresponding receiving grooves 323. Continued rotationin excess of the torque limits can again result in disengagement of theslip-clutch device 320.

In other embodiments, the receiving grooves 323 of the drive plate 322and the projections 325 of the slip plate 324 may be formed withconfigurations similar to those illustrated in FIG. 3. Thus, if the slipplate 324 becomes disengaged from the drive plate 322 due to excessivetorque, only a partial rotation of the slip plate 324 will be requiredbefore a projection 325 mates with a receiving groove 323 and theslip-clutch device 320 is reengaged. Accordingly, a specific or desiredamount of rotation of the slip plate 324 can be contemplated beforereengagement with the drive plate 322 takes place. The particular amountof rotation can be determined or designed by the relative configurationof the receiving grooves 323 and projections 325 of the slip-clutchplates.

Other embodiments of the present invention may include alternativeslip-clutch configurations. For example, a slip-clutch device 320 mayinclude ball bearings or cylindrical bearings that fit within holes of aslip-clutch plate that is, in turn, removably attached to the drivemechanism 380. Upon application of excessive force, the ball bearings orcylindrical bearings may slip out of the holes, disengaging theslip-clutch device 320. Other slip-clutch devices 320, as known, canalso be used with embodiments of the present invention.

A defeater spacer 330 may be removably or permanently fixed to theslip-clutch device 320 for imparting movement to the slip plate 324 ofthe slip-clutch device. Alternatively, other mechanisms for impartingrotational forces from a handwheel 100 or actuator to the slip-clutchdevice 320 may be employed with embodiments of the present invention.The defeater spacer 330 illustrated in FIG. 2 may also includevertically oriented teeth capable of receiving mating verticallyoriented teeth of a pressure nut 360. According to certain embodimentsof the present invention, the attachment of the defeater spacer 330 tothe slip-clutch device 320 permits springs 350 to be placed within theinterior space or a spring set space of the housing 310 and in contactwith the slip-clutch device 320.

One or more springs 350 may be placed within the interior space of thehousing 310 over the slip-clutch device 320. In some embodiments, thesprings 350 can be positioned in a space defined by a defeater spacer330 and an interior wall of the housing 310. The upper boundary of thespace may be defined by a pressure nut 360, as illustrated in FIG. 2,while the lower boundary of the space may be defined by an upper surfaceof the slip plate 324. The springs 350 exert a force on the slip plate324.

According to embodiments of the invention, the amount of force exertedby springs 350 on the slip plate 324 may be altered by increasing ordecreasing the number, size, or force of the springs 350 used. Forexample, the springs 350 illustrated in FIG. 2 include three Bellevillesprings placed in series. Other combinations of Belleville springs inseries, parallel, or a combination of series and parallel could also beused to achieve the desired force for the torque limiting device 300. Inaddition, shims or other components could be combined with the springs350 to adjust the amount of force exerted upon the slip-clutch device320. It is understood that many different types of springs 350 or othercomponents could be used in place of the Belleville springs illustratedin FIG. 2 and that such use is encompassed by the present invention.

As illustrated in FIG. 2, a pressure nut 360 is positioned in theinterior space of the housing 310. The pressure nut 360 is capable ofrotating within the housing 310 and is in communication with thehandwheel 100 or with an actuator. As the handwheel 100 or actuatorrotates, the pressure nut 360 also rotates. An o-ring 362 may beincluded in communication with the pressure nut 360 and the housing 310.The pressure nut 360 may also be in communication with the defeaterspacer 330 and is capable of tuning the defeater spacer 330 to impartrotation to the slip-clutch device 320 as a result of the rotation of ahandwheel 100 or an actuator. In some embodiments, the pressure nut 360may include a flange 360A that may have vertically oriented teethcapable of fitting with the vertically oriented teeth of the defeaterspacer 330. Rotation of the pressure nut 360 imparts a force on theflange 360A which, in turn, imparts a force on the defeater spacer 330,rotating the defeater spacer 330 in the same direction as the pressurenut 360. Rotation of the defeater spacer 330 imparts a rotational forceon the slip plate 324, thereby turning the slip-clutch device 320 aslong as the torque limits of the torque limiting device 300 are notexceeded.

An attachment 370 can be removably connected to the housing 310 by bolts375. The attachment 370 may hold the pressure nut 360 in a desiredposition within the housing 310. The size and placement of theattachment 370 may dictate where the pressure nut 360 is located withinthe housing 310.

The pressure nut 360 may also define the upper bounds of the spacewithin which the springs 350 in the housing 310 may move. As illustratedin FIG. 2, the upper bounds of the space containing springs 350 isdefined by the pressure nut 360. If the pressure nut 360 is adjustedupwards, less force is placed on the springs 350. If the pressure nut360 is adjusted, or positioned, further into the housing 310, thenadditional force is applied to the springs 350. The amount of forceexerted by springs 350 corresponds to the torque limits that will beallowed by the torque limiting device 300 because the force exerted bysprings 350 holds the slip plate 324 in place. If the amount of torqueplaced on the slip-clutch device 320 exceeds the amount of force appliedto the slip plate 324, the slip plate 324 will slip from its matingposition with the drive plate 322, thereby preventing further movementof drive mechanism 380.

According to embodiments of the present invention, the torque limits ofthe torque limiting device 300 may be adjusted in numerous ways. Forexample, the torque limits may be adjusted by selecting the type andstrength of springs 350 placed in the housing 310. In other instances,the torque limit may be adjusted by positioning the pressure nut 360 ata desired location within the housing 310 to impart a desired forceagainst the springs 350 and the slip-clutch device 320.

According to some embodiments of the invention, a slip-clutch overridemechanism is provided. The slip-clutch override mechanism holds theslip-clutch device 320 in a fixed position, preventing the slip-clutchdevice 320 from slipping. When engaged, the slip-clutch overridemechanism allows an amount of torque greater than the torque limits ofthe torque limiting device 300 to be imparted to the valve assembly 200.

For example, a representative slip-clutch override mechanism accordingto a particular embodiment of the invention is illustrated in FIG. 2.The slip-clutch override mechanism includes one or more pins 410positioned within one or more openings in the housing 310 of the torquelimiting device 300. The openings in the housing 310 correspond to thepositioning of the slip plate 324 within the housing 310. The sideportion of the slip plate 324 next to the housing 310 includes a groove326 within which the pins 410 may fit when the slip plate 324 is matedwith the drive plate 322. In other words, when the projections 325 ofthe slip plate 324 are positioned in the receiving grooves 323 of thedrive plate 322, the groove 326 in the slip plate 324 corresponds to andaligns with the openings in the housing 310. Exerting a force upon thepins 410 towards the housing 310 may force the pins 410 into the groove326 of the slip plate 324. When the pins 410 are positioned in thegroove 326 of the slip plate 324, the slip plate 324 is locked in amated position with the drive plate 322. For example, activation of thepins 410 secures the slip plate 324 in a mated position with the driveplate 322, preventing the slip plate 324 from slipping and allowing anincreased amount of torque to be applied to the valve assembly. Thus,activation of the slip-clutch override mechanism will allow an amount oftorque greater than the torque limits of the torque limiting device 300to be applied to the valve assembly 200.

In other embodiments of the invention, the pins 410 may be positioned inholes in the housing 310 which are directly above the slip plate 324.Activation of the pins 410 into the housing 310 positions the pins 410directly above the slip plate 324 to prevent movement of the slip plate324. In this fashion, an increased amount of torque may be applied tothe valve assembly 300 when the pins 410 have been activated.

In yet other embodiments, a pin may be deployed through the pressure nut360 to exert a force on the slip plate 324, which locks the slip plate324 in a mated position with the drive plate 322.

According to still other embodiments of the invention, additionalmechanisms may be used to override the slip-clutch device 320 and allowtorque to be applied to a valve assembly which torque exceeds the torquelimits of the torque limiting device 300.

Embodiments of the invention may additionally include a “tattletale”indicator or device for determining whether the torque limits on a valveassembly 200 have been, or may have been, exceeded. For example, withembodiments of the invention employing the slip-clutch overridemechanism illustrated in FIG. 2, the pins 410 may be configured suchthat, once deployed, they are permanently positioned in the lockingposition. Thus, visual inspection of the positioning of the pinsindicates that the torque limitations of the valve assembly 200 may havebeen exceeded.

In other embodiments, the openings in the housing 310 containing thepins 410 may include breakable seals which are intact until one or morepins 410 are activated to engage the slip-clutch override mechanism.Upon activation of a pin 410 into the groove 326 of the slip plate 324,the breakable seal (not shown) is broken. Even if an activated pin 410is pulled out to its original position, the broken seal will act as atattletale, indicating that at some point, the slip-clutch overridemechanism had been activated and that the torque limits of the valveassembly 200 may have been exceeded.

In other embodiments, the tattletale may include an indicator in thegroove 326 of the slip plate 324. For example, a soft material, such aswax or other substance, may be positioned in a portion of the groove326. Upon activation of a pin 410, at least a portion of the softmaterial may be displaced, moved, or disturbed, such that upondisassembly of the torque limiting device 300, visual inspection of thesoft material in the groove 326 will indicate the disturbance and theprevious activation of the slip-clutch override mechanism.

In still other embodiments, the tattletale may be constructed of acrushable material. In some instances, the crushable material may becrushed by the activation of a pin 410. In other instances, thecrushable material may be selected such that it will be crushed upon anexertion of an amount of torque exceeding the torque limits of the valveassembly 200. Such a material may be inserted between the slip-clutchdevice 320 and the drive mechanism 380, or at another position withinthe torque limiting device 300.

According to particular embodiments of the invention, other tattletaledevices may also be used. For example, any torque limiting device 300including a tattletale or an equivalent device or mechanism thatindicates that the slip-clutch override mechanism has been activated isencompassed by the present invention.

Although the illustrated embodiments show one type of valve assembly anda single configuration of a torque limiting device 300, it is understoodthat the torque limiting devices 300 of the present invention may beconfigured to fit numerous valve assemblies 200, regardless of the size,shape, configuration, or design of such assembly.

It is understood that illustrated handwheel 100 represents a single typeand configuration of a handwheel 100. Torque limiting devices 300according to the present invention may be modified or configured to fithandwheels 100 having different sizes, shapes, and configurations thanthe handwheel 100 illustrated in FIG. 2. Further, the handwheel 100 usedwith embodiments of the invention may be replaced by a handle or otherdevice capable of applying a rotational or other force to the torquelimiting device 300. In addition, torque limiting devices 300 accordingto embodiments of the present invention may be modified or configured tofit valve assemblies 200 employing the use of actuators instead of, orin addition to, handwheels.

Having thus described certain currently preferred embodiments of thepresent invention, it is understood that the invention defined by theappended claims is not to be limited by particular details or examplesset forth in the above description, as many apparent variations thereofare contemplated without departing from the spirit or scope thereof ashereinafter claimed.

1. A torque limiting device for a valve assembly, comprising: a housing;a slip-clutch device positioned within the housing; a force generatingdevice positioned within the housing and imparting a force on theslip-clutch device; and an override mechanism in communication with thehousing, wherein the override mechanism may be activated to preventslippage of the slip-clutch device.
 2. The torque limiting device ofclaim 1, wherein the force generating device comprises at least onespring.
 3. The torque limiting device of claim 1, wherein the forcegenerating device comprises at least one Belleville spring.
 4. Thetorque limiting device of claim 1, wherein the slip-clutch devicecomprises: a slip plate; and a drive plate in communication with theslip plate.
 5. The torque limiting device of claim 4, wherein the driveplate further comprises a drive mechanism integrated with the driveplate for driving a valve stem.
 6. The torque limiting device of claim1, wherein the override mechanism comprises at least one pin positionedin a hole in the housing and extending outside the housing.
 7. Thetorque limiting device of claim 1, wherein the override mechanismcomprises: a hole in the housing, wherein the hole extends from an outerportion of the housing to an interior portion of the housing; and a pinpositioned part way through the hole in the housing, wherein thepositioning of the pin does not extend to an interior portion of thehousing.
 8. The torque limiting device of claim 7, further comprising aplurality of holes having a plurality of pins positioned part waytherein.
 9. The torque limiting device of claim 7, further comprising abreakable seal positioned in the hole between the interior portion ofthe housing and an end of the pin positioned part way through the hole,wherein activation of the override mechanism breaks the breakable seal.10. The torque limiting device of claim 7, wherein the hole ispositioned just above the slip-clutch device such that activation of theoverride mechanism positions the pin into an interior portion of thehousing above the slip-clutch device and prevents the slip-clutch devicefrom slipping.
 11. The torque limiting device of claim 7, wherein thehole is positioned adjacent to the slip-clutch device in the housingsuch that activation of the override mechanism engages the pin with theslip-clutch device preventing slippage of the slip-clutch device. 12.The torque limiting device of claim 1 further comprising a tattletaledevice, wherein the tattletale device indicates whether the overridemechanism has been activated.
 13. The torque limiting device of claim12, wherein the tattletale device comprises a crushable material that iscrushed when the override mechanism is activated.
 14. The torquelimiting device of claim 12, wherein the tattletale device comprises asoft material that is moved or displaced when the override mechanism isactivated.
 15. The torque limiting device of claim 12, wherein thetattletale device comprises a seal that is broken when the overridemechanism is activated.
 16. The torque limiting device of claim 1,further comprising a pressure nut moveably positioned in the housing,wherein movement of the pressure nut alters a force applied to theslip-clutch device.
 17. The torque limiting device of claim 1, furthercomprising: a handwheel; and a valve assembly, wherein the torquelimiting device is coupled between the handwheel and the valve assemblyto limit the amount of torque applied to the valve assembly by thehandwheel.
 18. A torque limiting device, comprising: a housing having anouter surface and a substantially cylindrical inner surface; asubstantially planar drive plate disposed within the housing at a fixedlongitudinal position therein, wherein the drive plate comprises anouter cylindrical surface disposed adjacent the substantiallycylindrical inner surface of the housing and at least one receivinggroove; a substantially planar slip plate disposed within the housingadjacent the drive plate, wherein the slip plate is moveable in alongitudinal direction within the housing and comprises an outercylindrical surface disposed adjacent the inner surface and at least oneprojection for mating with the at least one receiving groove of thedrive plate; at least one spring configured to press the slip plateagainst the drive plate; and an override mechanism in a deactivatedposition, wherein the override mechanism is configured to prevent thelongitudinal movement of the slip plate when activated.
 19. The torquelimiting device of claim 18, wherein the override mechanism furthercomprises: at least one passage extending through the housing outersurface and substantially cylindrical inner surface; and at least onepin positioned partially into the at least one passage, wherein the pindoes not extend beyond the substantially cylindrical inner surface. 20.The torque limiting device of claim 18, further comprising a tattletaledevice, wherein the tattletale device evidences activation of theoverride mechanism.
 21. A method for limiting torque applied to a valveassembly, comprising: providing a torque limiting device coupled to avalve assembly to limit the amount of torque that may be applied to thevalve assembly; and providing an override mechanism for overriding thetorque limiting device.
 22. The method of claim 21, further comprisingproviding a tattletale device for indicating activation of the overridemechanism.